1. Field of the Invention
The present invention relates to a fuel cell. More particularly, the invention relates to a fuel cell with its cells disposed in a planar arrangement and a method for connecting current collectors thereto.
2. Description of the Related Art
A fuel cell is a device that generates electricity from hydrogen and oxygen so as to obtain highly efficient power generation. A principal feature of the fuel cell is its capacity for direct power generation which does not undergo a stage of thermal energy or kinetic energy as in the conventional power generation. This presents such advantages as high power generation efficiency despite the small scale setup, reduced emission of nitrogen compounds and the like, and environmental friendliness on account of minimal noise or vibration. In this manner, the fuel cells are capable of efficiently utilizing chemical energy in its fuel and, as such, environmentally friendly. Fuel cells are therefore expected as an energy supply system for the twenty-first century and have gained attention as a promising power generation system that can be used in a variety of applications including space applications, automobiles, mobile devices, and large and small scale power generation. Serious technical efforts are being made to develop practical fuel cells.
Known as one of such fuel cells described above is a polymer electrolyte fuel cell (PEFC) that operates at a low temperature of less than or equal to 100° C. As one type of this PEFC, known are a type where hydrogen is used as a fuel, a type where a direct methanol fuel cell (DMFC) where methanol water solution as a fuel is not reformed and is directly supplied to the anode so as to produce the electric power by an electrochemical reaction induced between the methanol water solution and oxygen, and the like. It is expected that PEFC will be used in power supplies for mobile devices such as cell phones, notebook-size personal computers, PDAs, MP3 players, digital cameras, electronic dictionaries and books.
With a conventional planar fuel cell, in which the cells are disposed in a planar arrangement, the terminal of a current collector is extended to an end of an electrolyte membrane in order to electrically connect adjacent cells with each other by a connector (interconnector). This configuration has resulted in an area of a current collector larger than necessary and a long terminal of the current collector, which leads to a proportionately larger resistance.
Also, as a known example, there is a structure in which an interconnector is provided in a through-hole in an electrolyte membrane between adjacent cells. However, this structure can present a problem when the compactness of the fuel cell is the primary concern. That is, as the distance between the electrodes are reduced, there can occur shorts between the adjacent electrodes or cross leaks in the through-hole area.